His father is English and his mother Irish. He is the brother of Simon Easterby, also an Ireland international and the most capped back-rower to come from Yorkshire.
Easterby made his senior Ireland debut against the United States on 10 June 2000 and marked the occasion by scoring two tries in an 83–3 victory. Easterby made his test debut in the same year as Peter Stringer but has always trailed the Munster scrum-half in the Irish pecking order. 21 out of his 27 appearances before the 2005 Six Nations Championship were made as a substitute. He enjoyed a stint with London Scottish after enjoying his most successful part of his career with Rotherham in the English Premiership and with Leinster in Ireland. He retired after the 2006/2007 season however made his comeback against Edinburgh Rugby on the 15 December 2007